Wavelength demultiplexer using the spatial dispersion of repeated-period double-chirped structures

Based on the rudimentary double-chirped stack, exploiting wavelength-dependent penetration depth, repeated-period double-chirped structures, in which each couple of Bragg layers is repeated for different times, are presented to increase the spatial linear shift and the beam shifting with different incident wavelength, thus allowing the design of compact thin-film spatial wavelength demultiplexer. We compare the improved structure repeated for n times with the directly double -chirped structure with the same layer number, finding that the former has not only more advantages in theoretical design but a higher tolerance in experiment al fabrication. Besides, we have given the qualitative analysis for the strongosc illation appearing in the spatial dispersion curves when the repeated times of improved double-chirped structure or the wavelength of incident beam are relatively large.